Scan2CAD raster to vector conversion software

REVIEW:

Colortrac SmartLF Ci 40 large format scanner

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Scanning in Greyscale

CAD users will not normally need to scan in greyscale, however we mention it briefly here out of interest.

In our review of the Graphtec CSX300 we noted that by default, the CSX300 scans monochrome images using its green LED only (greenscale), but that it includes a Gray Balance option that allows it to scan monochrome using red, green and blue LEDs. The images produced by the red, green and blue LED option give a result that agrees better with the human perception of how colours should look when represented in greyscale.

If you look at the Ci 40 scans below, you can see that the green and red threads show as different colours in the greyscale image. This indicates that the Ci 40 is scanning monochrome using red, green and blue LEDs. If it was scanning in greenscale, the red and green threads would both appear to be the same colour.

For more details, see our Graphtec CSX300 review.

Scanning in Colour

Colortrac does not recommend its Ci 40 large format scanners to users who require high quality colour scans of artwork, photographs and the like. For these types of application, Colortrac recommends its Gx and Gx+ series scanners, which use CCD technology.

However, the Ci 40's colour capability is more than adequate for CAD and GIS use and shows a marked improvement over the colour quality of Colortrac's SmartLF Cx 40 scanner.

CAD and GIS users will need to scan in colour if they are scanning coloured technical drawings and maps. There are also some original drawings that are simply too poor quality to scan in black and white without losing a lot of information. These drawings are often best scanned in greyscale or colour so that at least the information on them remains legible and usable, even if it will never be possible to (for example) use the scans for automatic raster to vector conversion.

Scanworks includes three colour options:

  • RGB (16.7 million colours)
  • 256 colours
  • 16 colours

When you are scanning in colour, you can either scan with sRGB on or off (raw).

When you scan with sRGB off, the Ci 40 stores each colour as scanned. When you scan with sRGB on, each scanned colour is mapped to a colour within the standard sRGB colour range. We found that sRGB scans (left, below) contained less detail than raw scans (right, below) and that there were some colour shifts.

Colortrac says it is working on improving its sRGB profile.

 
sRGB Raw RGB

The RGB option includes white point and black point settings, brightness and contrast options, and RGB curves. White point and black point settings allow you to ensure that the paper background is pure white and that the black parts of the document are pure black. RGB curves let you increase colour saturation and boost ranges of colours.

As 256 and even 16 colours are more than enough for most CAD or GIS and mapping applications, you may prefer to scan using the 256 or 16 colour options. The advantage is that 256 and 16 colour files are much smaller when opened up in any application.

You can determine the colours used in the 256 and 16 colour options either by a palette that you assign, or automatically. Using the palette option, you choose which colours (palette) will be used. ScanWorks is provided with a default palette and you can also create your own palette using ScanWorks' Colour Classification feature. Using the automatic option, ScanWorks chooses the 256 or 16 colours that it thinks best match the colours on the drawing.

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